KH

The K homology (KH) domain was first identified in the human heterogeneous nuclear ribonucleoprotein (hnRNP) K. An evolutionarily conserved sequence of around 70 amino acids, the KH domain is present in a wide variety of nucleic acid-binding proteins. The KH domain binds RNA, and can function in RNA recognition [(PUBMED:17437720)]. It is found in multiple copies in several proteins, where they can function cooperatively or independently. For example, in the AU-rich element RNA-binding protein KSRP, which has 4 KH domains, KH domains 3 and 4 behave as independent binding modules to interact with different regions of the AU-rich RNA targets [(PUBMED:17437720)]. The solution structure of the first KH domain of FMR1 [(PUBMED:9302998)] and of the C-terminal KH domain of hnRNP K [(PUBMED:10369774)] determined by nuclear magnetic resonance (NMR) revealed a beta-alpha-alpha-beta-beta-alpha structure. Proteins containing KH domains include:

The structure of a Nova protein K homology (KH) domain recognizing single-stranded RNA has been determined at 2.4 A resolution. Mammalian Nova antigens (1 and 2) constitute an important family of regulators of RNA metabolism in neurons, first identified using sera from cancer patients with the autoimmune disorder paraneoplastic opsoclonus-myoclonus ataxia (POMA). The structure of the third KH domain (KH3) of Nova-2 bound to a stem loop RNA resembles a molecular vise, with 5'-Ura-Cyt-Ade-Cyt-3' pinioned between an invariant Gly-X-X-Gly motif and the variable loop. Tetranucleotide recognition is supported by an aliphatic alpha helix/beta sheet RNA-binding platform, which mimics 5'-Ura-Gua-3' by making Watson-Crick-like hydrogen bonds with 5'-Cyt-Ade-3'. Sequence conservation suggests that fragile X mental retardation results from perturbation of RNA binding by the FMR1 protein.

Dissecting FMR1, the protein responsible for fragile X syndrome, in its structural and functional domains.

RNA. 1999; 5: 1248-58

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FMR1 is an RNA-binding protein that is either absent or mutated in patients affected by the fragile X syndrome, the most common inherited cause of mental retardation in humans. Sequence analysis of the FMR1 protein has suggested that RNA binding is related to the presence of two K-homologous (KH) modules and an RGG box. However, no attempt has been so far made to map the RNA-binding sites along the protein sequence and to identify possible differential RNA-sequence specificity. In the present article, we describe work done to dissect FMR1 into regions with structurally and functionally distinct properties. A semirational approach was followed to identify four regions: an N-terminal stretch of 200 amino acids, the two KH regions, and a C-terminal stretch. Each region was produced as a recombinant protein, purified, and probed for its state of folding by spectroscopical techniques. Circular dichroism and NMR spectra of the N-terminus show formation of secondary structure with a strong tendency to aggregate. Of the two homologous KH motifs, only the first one is folded whereas the second remains unfolded even when it is extended both N- and C-terminally. The C-terminus is, as expected from its amino acid composition, nonglobular. Binding assays were then performed using the 4-nt homopolymers. Our results show that only the first KH domain but not the second binds to RNA, and provide the first direct evidence for RNA binding of both the N-terminal and the C-terminal regions. RNA binding for the N-terminus could not be predicted from sequence analysis because no known RNA-binding motif is identifiable in this region. Different sequence specificity was observed for the fragments: both the N-terminus of the protein and KH1 bind preferentially to poly-(rG). The C-terminal region, which contains the RGG box, is nonspecific, as it recognizes the bases with comparable affinity. We therefore conclude that FMR1 is a protein with multiple sites of interaction with RNA: sequence specificity is most likely achieved by the whole block that comprises the first approximately 400 residues, whereas the C-terminus provides a nonspecific binding surface.

Three-dimensional structure and stability of the KH domain: molecular insights into the fragile X syndrome.

Cell. 1996; 85: 237-45

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The KH module is a sequence motif found in a number of proteins that are known to be in close association with RNA. Experimental evidence suggests a direct involvement of KH in RNA binding. The human FMR1 protein, which has two KH domains, is associated with fragile X syndrome, the most common inherited cause of mental retardation. Here we present the three-dimensional solution structure of the KH module. The domain consists of a stable beta alpha alpha beta beta alpha fold. On the basis of our results, we suggest a potential surface for RNA binding centered on the loop between the first two helices. Substitution of a well-conserved hydrophobic residue located on the second helix destroys the KH fold; a mutation of this position in FMR1 leads to an aggravated fragile X phenotype.

Essential role for KH domains in RNA binding: impaired RNA binding by a mutation in the KH domain of FMR1 that causes fragile X syndrome.

Cell. 1994; 77: 33-9

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The KH domain is an evolutionarily conserved sequence motif present in many RNA-binding proteins, including the pre-mRNA-binding (hnRNP) K protein and the fragile X mental retardation gene product (FMR1). We assessed the role of KH domains in RNA binding by mutagenesis of KH domains in hnRNP K and FMR1. Conserved residues of all three hnRNP K KH domains are required for its wild-type RNA binding. Interestingly, while fragile X syndrome is usually caused by lack of FMR1 expression, a previously reported mutation in a highly conserved residue of one of its two KH domains (Ile-304-->Asn) also results in mental retardation. We found that the binding of this mutant protein to RNA is severely impaired. These results demonstrate an essential role for KH domains in RNA binding. Furthermore, they strengthen the connection between fragile X syndrome and loss of the RNA binding activity of FMR1.

Disease (disease genes where sequence variants are found in this domain)

This information is based on mapping of SMART genomic protein database to KEGG orthologous groups. Percentage points are related to the number of proteins with KH domain which could be assigned to a KEGG orthologous group, and not all proteins containing KH domain. Please note that proteins can be included in multiple pathways, ie. the numbers above will not always add up to 100%.

STRUCTURE OF THE THERMUS THERMOPHILUS 30S RIBOSOMAL SUBUNIT IN COMPLEX WITH A MESSENGER RNA FRAGMENT AND COGNATE TRANSFER RNA ANTICODON STEM-LOOP BOUND AT THE A SITE AND WITH THE ANTIBIOTIC PAROMOMYCIN

Structure of the Thermus thermophilus 30S ribosomal subunit in the presence of codon and crystallographically disordered near-cognate transfer rna anticodon stem-loop mismatched at the first codon position

Structure of the Thermus thermophilus 30S ribosomal subunit in the presence of crystallographically disordered codon and near-cognate transfer RNA anticodon stem-loop mismatched at the second codon position

Crystal Structure of a Streptomycin Dependent Ribosome from E. Coli, 30S Subunit of 70S Ribosome. THIS FILE, 1PNS, CONTAINS THE 30S SUBUNIT, TWO TRNAS, AND ONE MRNA MOLECULE. THE 50S RIBOSOMAL SUBUNIT IS IN FILE 1PNU.

Structure of the ribosomal 80S-eEF2-sordarin complex from yeast obtained by docking atomic models for RNA and protein components into a 11.7 A cryo-EM map. This file, 1S1H, Contains 40S subunit. The 60S Ribosomal Subunit Is In File 1S1I.

Crystal structure of five 70s ribosomes from Escherichia Coli in complex with protein Y. This file contains the 30s subunit of one 70s ribosome. The entire crystal structure contains five 70s ribosomes and is described in remark 400.

Crystal structure of five 70s ribosomes from Escherichia Coli in complex with protein Y. This file contains the 30s subunit of one 70s ribosome. The entire crystal structure contains five 70s ribosomes and is described in remark 400.

Crystal structure of five 70s ribosomes from Escherichia Coli in complex with protein Y. This file contains the 30s subunit of one 70s ribosome. The entire crystal structure contains five 70s ribosomes and is described in remark 400.

Crystal structure of five 70s ribosomes from Escherichia Coli in complex with protein Y. This file contains the 30s subunit of one 70s ribosome. The entire crystal structure contains five 70s ribosomes and is described in remark 400.

Crystal structure of five 70s ribosomes from Escherichia Coli in complex with protein Y. This file contains the 30s subunit of one 70s ribosome. The entire crystal structure contains five 70s ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from escherichia coli in complex with the antibiotic kasugamyin at 3.5A resolution. this file contains the 30s subunit of one 70s ribosome. the entire crystal structure contains two 70s ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from escherichia coli in complex with the antibiotic kasugamyin at 3.5a resolution. this file contains the 30s subunit of one 70s ribosome. the entire crystal structure contains two 70s ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli at 3.5 A resolution. This file contains the 30S subunit of one 70S ribosome. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli at 3.5 A resolution. This file contains the 30S subunit of the second 70S ribosome. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

30S ribosomal subunit, tRNAs, mRNA and release factor RF1 from a crystal structure of the whole ribosomal complex. This file contains the 30S subunit, tRNAs, mRNA and release factor RF1 from a crystal structure of the whole ribosomal complex"". The entire crystal structure contains one 70S ribosome, tRNAs, mRNA and release factor RF1 and is described in remark 400.

30S ribosomal subunit, tRNAs and mRNA from a crystal structure of the whole ribosomal complex with a stop codon in the A-site. This file contains the 30S subunit, tRNAs and mRNA from a crystal structure of the whole ribosomal complex with a stop codon in the A-site and is described in remark 400.

Crystal Structure of Ribosome with messenger RNA and the Anticodon stem-loop of P-site tRNA. This file contains the 30s subunit of one 70s ribosome. The entire crystal structure contains two 70s ribosomes and is described in remark 400.

Crystal Structure of Ribosome with messenger RNA and the Anticodon stem-loop of P-site tRNA. This file contains the 30s subunit of one 70s ribosome. The entire crystal structure contains two 70s ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with neomycin. This file contains the 30S subunit of the first 70S ribosome, with neomycin bound. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with neomycin. This file contains the 30S subunit of the second 70S ribosome, with neomycin bound. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with gentamicin. This file contains the 30S subunit of the first 70S ribosome, with gentamicin bound. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with gentamicin. This file contains the 30S subunit of the second 70S ribosome, with gentamicin bound. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with ribosome recycling factor (RRF). This file contains the 30S subunit of the first 70S ribosome. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with ribosome recycling factor (RRF). This file contains the 30S subunit of the second 70S ribosome. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with gentamicin and ribosome recycling factor (RRF). This file contains the 30S subunit of the first 70S ribosome, with gentamicin bound. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with gentamicin and ribosome recycling factor (RRF). This file contains the 30S subunit of the second 70S ribosome, with gentamicin bound. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with spectinomycin. This file contains the 30S subunit of the first 70S ribosome, with spectinomycin bound. The entire crystal structure contains two 70S ribosomes.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with spectinomycin. This file contains the 30S subunit of the second 70S ribosome, with spectinomycin bound. The entire crystal structure contains two 70S ribosomes.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with spectinomycin and neomycin. This file contains the 30S subunit of the first 70S ribosome, with spectinomycin and neomycin bound. The entire crystal structure contains two 70S ribosomes.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with spectinomycin and neomycin. This file contains the 30S subunit of the second 70S ribosome, with spectinomycin and neomycin bound. The entire crystal structure contains two 70S ribosomes.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with paromomycin and ribosome recycling factor (RRF). This file contains the 30S subunit of the first 70S ribosome, with paromomycin bound. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with paromomycin and ribosome recycling factor (RRF). This file contains the 30S subunit of the second 70S ribosome, with paromomycin bound. The entire crystal structure contains two 70S ribosomes and is described in remark 400.

Structural basis for translation termination on the 70S ribosome. This file contains the 30S subunit, release factor 1 (RF1), two tRNA, and mRNA molecules of one 70S ribosome. The entire crystal structure contains two 70S ribosomes as described in remark 400.

Structural basis for translation termination on the 70S ribosome. This file contains the 30S subunit, release factor 1 (RF1), two tRNA, and mRNA molecules of the second 70S ribosome. The entire crystal structure contains two 70S ribosomes as described in remark 400.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with hygromycin B. This file contains the 30S subunit of the first 70S ribosome, with hygromycin B bound. The entire crystal structure contains two 70S ribosomes.

Crystal structure of the bacterial ribosome from Escherichia coli in complex with hygromycin B. This file contains the 30S subunit of the second 70S ribosome, with hygromycin B bound. The entire crystal structure contains two 70S ribosomes.

Crystal structure of a translation termination complex formed with release factor RF2. This file contains the 30S subunit, RF2, two tRNA, and mRNA molecules of one 70S ribosome. The entire crystal structure contains two 70S ribosomes as described in remark 400.

Crystal structure of a translation termination complex formed with release factor RF2. This file contains the 30S subunit, RF2, two tRNA, and mRNA molecules of the second 70S ribosome. The entire crystal structure contains two 70S ribosomes as described in remark 400.

Elongation complex of the 70S ribosome with three tRNAs and mRNA. This entry 3I8G contains 30S ribosomal subnit.The 50S ribosomal subunit can be found in PDB entry 3I8F. Molecule B in the same asymmetric unit is deposited as 3I8G (30S) and 3I8F (50S).

Elongation complex of the 70S ribosome with three tRNAs and mRNA.This entry 3I8H contains 30S ribosomal subnit. The 50S ribosomal subunit can be found in PDB entry 3I8I. Molecule A in the same asymmetric unit is deposited as 3I8F (50S) and 3I8G (30S).

Initiation complex of 70S ribosome with two tRNAs and mRNA. This entry 3I9B contains 30S ribosomal subunit of molecule B. The 50S ribosomal subunit can be found in PDB entry 3I9C. Molecule A in the same asymmetric unit is deposited as 3I9D (30S) and 3I9E (50S)

Initiation complex of 70S ribosome with two tRNAs and mRNA. This entry 3I9D contains 30S ribosomal subunit of molecule A. The 50S ribosomal subunit can be found in PDB entry 3I9E. Molecule B in the same asymmetric unit is deposited as 3I9B (30S) and 3I9C (50S)

Structural insights into cognate vs. near-cognate discrimination during decoding. This entry contains the small subunit of a ribosome programmed with a near-cognate codon, A/T-site tRNA, P-site tRNA, mRNA and EF-Tu

Recognition of the amber stop codon by release factor RF1. This entry 3MR8 contains 30S ribosomal subunit. The 50S ribosomal subunit can be found in PDB entry 3MS1. Molecule B in the same asymmetric unit is deposited as 3MRZ (50S) and 3MS0 (30S).

Recognition of the amber stop codon by release factor RF1. This entry 3MS0 contains 30S ribosomal subunit. The 50S ribosomal subunit can be found in PDB entry 3MRZ. Molecule A in the same asymmetric unit is deposited as 3MR8 (30S) and 3MS1 (50S).

Structure of the Thermus thermophilus 30S ribosomal subunit complexed with a human anti-codon stem loop (HASL) of transfer RNA lysine 3 (tRNALys3) bound to an mRNA with an AAA-codon in the A-site and Paromomycin

Structure of the Thermus thermophilus 30S ribosomal subunit complexed with a human anti-codon stem loop (HASL) of transfer RNA Lysine 3 (TRNALYS3) bound to an mRNA with an AAG-codon in the A-site and paromomycin

The structure of thermorubin in complex with the 70S ribosome from Thermus thermophilus. This file contains the 30S subunit of one 70S ribosome. The entire crystal structure contains two 70S ribosomes.

The structure of thermorubin in complex with the 70S ribosome from Thermus thermophilus. This file contains the 30S subunit of one 70S ribosome. The entire crystal structure contains two 70S ribosomes.'

Crystal structure analysis of ribosomal decoding. this entry contains the 30S ribosomal subunit of the second 70S molecule in the asymmetric unit for the near-cognate trna-leu complex with paromomycin.

Structure of the Thermus thermophilus 30S ribosomal subunit complexed with a human mitochondrial anticodon stem loop (ASL) of transfer RNA Methionine (TRNAMET) bound to an mRNA with an AUG-codon in the A-site and paromomycin.

Structure of the Thermus thermophilus 30S ribosomal subunit complexed with a human mitochondrial anticodon stem loop (ASL) of transfer RNA Methionine (TRNAMET) bound to an mRNA with an AUA-codon in the A-site and paromomycin

70S ribosome translocation intermediate GDPNP-I containing elongation factor EFG/GDPNP, mRNA, and tRNA bound in the pe*/E STATE. This entry contains the 30S ribosomal subunit A. The 50S subunit a can be found in 4KCZ. Molecule B in the same asymmetric unit is deposited as 4KD0 (30S) and 4KD2 (50S)

70S Ribosome translocation intermediate GDPNP-I containing elongation factor EFG/GDPNP, MRNA, AND TRNA BOUND IN THE pe*/E STATE. THIS ENTRY CONTAINS THE 30S RIBOSOMAL SUBUNIT B. THE 50S SUBUNIT B CAN BE FOUND IN 4KD2. MOLECULE A IN THE SAME ASYMMETRIC UNIT IS DEPOSITED AS 4KCY (30S) AND 4KCZ (50S)

70S Ribosome translocation intermediate FA-3.6A CONTAINING ELONGATION FACTOR EFG/FUSIDIC ACID/GDP, MRNA, AND TRNA BOUND IN THE pe*/E STATE. THIS ENTRY CONTAINS THE 30S RIBOSOMAL SUBUNIT A. THE 50S SUBUNIT A CAN BE FOUND IN 4KD9. MOLECULE B IN THE SAME ASYMMETRIC UNIT IS DEPOSITED AS 4KDA (30S) AND 4KDB (50S).

70S Ribosome translocation intermediate FA-3.6A CONTAINING ELONGATION FACTOR EFG/FUSIDIC ACID/GDP, MRNA, AND TRNA BOUND IN THE pe*/E STATE. THIS ENTRY CONTAINS THE 30S RIBOSOMAL SUBUNIT B. THE 50S SUBUNIT A CAN BE FOUND IN 4KDB. MOLECULE A IN THE SAME ASYMMETRIC UNIT IS DEPOSITED AS 4KD8 (30S) AND 4KD9 (50S).

70S Ribosome translocation INTERMEDIATE FA-4.2A CONTAINING ELONGATION FACTOR EFG/FUSIDIC ACID/GDP, MRNA, AND TRNA BOUND IN THE pe*/E STATE. THIS ENTRY CONTAINS THE 30S RIBOSOMAL SUBUNIT A. THE 50S SUBUNIT A CAN BE FOUND IN 4KDH. MOLECULE B IN THE SAME ASYMMETRIC UNIT IS DEPOSITED AS 4KDJ (30S) AND 4KDK (50S).

70S Ribosome translocation INTERMEDIATE FA-4.2A CONTAINING ELONGATION FACTOR EFG/FUSIDIC ACID/GDP, MRNA, AND TRNA BOUND IN THE pe*/E STATE. THIS ENTRY CONTAINS THE 30S RIBOSOMAL SUBUNIT B. THE 50S SUBUNIT B CAN BE FOUND IN 4KDK. MOLECULE A IN THE SAME ASYMMETRIC UNIT IS DEPOSITED AS 4KDG (30S) AND 4KDH (50S).